Using scan tool for car diagnose service

1
Using scan tool for car diagnose service

• Subtitle

2
Use an OBD II

• This is a late-model vehicle with whats known as
  OBD II, the second-generation on-board diagnostic
  system that replaced OBD I starting in 1994. Its
  industry-wide and federally mandated. One of the
  problems with OBD II for the do-it-yourselfer is
  that you cant get trouble codes by counting the
  blinkson the Check Engine light like you can on
  earlier computer-controlled vehicles. You could
  take your minivan into a high-tech shop, where
  the minimum charge for diagnosis and inspection
  could run you somewhere into three figures. Or
  youcan learn about OBD II yourself, but you will
  need a piece of diagnostic equipment that you
  probably dont havean OBD II scan tool. 

3

• If the Check Engine light came on, it should be
  no surprise that the vehicle failed an emissions
  test. With OBD II, that light comes on only if
  theres a failure that significantly affects
  emissions. That makes the scan tool even
  more important since it will reveal a lot of the
  problems that do not cause the warning light to
  come on.With many problems, the light stays on
  after the repair is made and the code remains in
  the computer memory for a certain number of
  ignition on/off cycles. Your daughter didnt
  tighten the gas cap correctly, causing a code for
  the evaporative emissions system to set.
  Eventually the light will go out and the code
  will self-erase, perhaps after the next time you
  start and stop the car. You also can use the scan
  tool to erase it immediately.

4

• With many other problems, however, the only way
  to turn off the light and erase the code is with
  the scan tool. Just a warning If you erase
  trouble codes with a scan tool or disconnect the
  battery for any reason, you also erase the
  computers continuous monitoring system. So if
  you take your car in for a state inspection
  before enough normal driving, the computer might
  not have completed all its tests, and your car
  will fail inspection for that reason.The OBD II
  scan tester not only will enable you to find
  answers to the simpler problems, but will tell
  you into what areas the seemingly more
  complicated ones fall. Then you will have a
  better understanding of what the technician is
  (or should be) looking for.

5
Cracking the Code

• With an OBD II scan tool used for car diagnostic
  service, you also can read a certain amount of
  engine operating data typically rpm, ignition
  timing, fuel-injection calibrations, readings
  from a variety of sensors (such as the oxygen,
  throttle position, barometric and mass airflow
  sensors), a calculated load value and sometimes
  switch position signals. OBD II also includes a
  capture mode, in which you can use the scan
  tool to take a snapshot of what the sensors
  were reading at the exact instanta driveability
  hiccup occurred.

6
Sensor Scan

• With enhanced scan tool capability, you can
  discover problems that do not trigger the
  engine-warning light. For example, we recently
  turned up a generic PO713 code on a late-model
  car. This is listed in the shop manual as
  transmission fluid temperature sensor
  circuithigh input. If the transmission fluid is
  running very hot, the transmission could
  completely fail, and quickly.it used for every
  car diagnostic service.A scan tool could save a
  lot of worry and effort if it has enhanced
  diagnostics. You can do much of the
  troubleshooting from the drivers seat the way we
  did. First we cleared the code with a simple push
  of a buttonon the tester. Then we rechecked
   the code came back quickly. We cleared it
  again and looked at the reading that was coming
  from the transmission temperature sensor to the
  powertrain computer. It was 131 F, nothing
  abnormal.The problem apparently was in the
  sensor or the circuit, possibly a bad connection.
  The wiring was good and when we started poking
  around, we found physical damage that clearly
  indicated the problem was a defective sensor.

7
Scan Tool Choices

• if you have a late-model vehicle, you have OBD
  II. However, just because its generic, and the
  wiring connector from any OBD II scan tool will
  plug into your vehicle, doesnt mean any OBD II
  scan tool will work on your car. The Europeans
  are the problem, as the latest ones (1998 and
  later) require a software upgrade. Korean cars
  are also problematic, and how well they work with
  any given scan tool needs to be investigated on a
  case-by-case basis.The OTC Mind Reader for OBD
  I can be upgraded with an additional chip to read
  generic OBD II in domestic, Japanese and earlier
  European models (but not the newest Europeans).

8

• The Actron ScanTool for OBD I can be updated to
  the same level of OBD II as the OTC Mind Reader
  with a plug-in cartridge (or you can buy an OBD
  II-only model).AutoXray produces a programmable
  scan tool. Although it doesnt have the OBD I
  Chrysler command tests of the Mind Reader, it is
  the one home mechanics scan tool weve tested to
  date that covers all generic OBD II models
  (including the Europeans) with more on the way.
  The software will be sold over the Internet.
  Youll be able to store it on your personal
  computer and then download it to your scan tool
  via a cable available from the manufacturer.

9

• Any AutoXray scan tool is designed to be upgraded
  electronically, from one-make OBD I coverage
  through the latest models. Although the
  professionals have had all this software (and a
  lot more) in their scan tools, you have to wait
  for it in the general consumer market. Other scan
  tools may be upgraded to enhanced status and
  beyond with new cartridges, CD-ROM or via the
  Internet.Although Actron has a line of OBD II
  scan tools, its top tester for car owners is the
  Actron CP9087, a simple code reader with
  read-codes and code-erase buttons. You get no
  sensor readings or other data items. Its a
  low-cost device (under 200) that comes with a
  good assortment of wire leads for making test
  connectionsincluding a back-probe adapter that
  has a thin, curved metal terminal. This terminal
  lets the probe slip through a water-sealed
  connector to reach a wiring terminal for a test
  connection.

10

• OBD II is entering its sixth full year and the
  earliest vehicles that have this system are off
  warranty. OBD II is complex and weve given you
  just a basic introduction. The OBD II powertrain
  computer is getting a lot better at finding
  problems and logging codes. But, the computer
  wont tell you a thing unless you hook up a scan
  tool.

11
How OBD II Transmits Data

• today's powertrain computers are at the heart of
  a vehicle's communications network, circulating
  information from switches and sensors to the
  other computers that control antilock brakes, air
  conditioning, transmission, suspension and safety
  systems.  The powertrain computer is also in
  charge of systems that affect engine emissions,
  so the information it processes has to be
  available for evaluation by a technician.  That
  information travels along a wire to a standard
  16-terminal diagnostic connector (although,
  generally, fewer than a half-dozen terminals are
  live in any given vehicle). Because manufacturers
  do not all use the same data transmission
  protocols, the scan tool must be programmed to
  recognize which one is being used.  Fortunately,
  there has been some standardization, but we're
  not down to one transmission protocol for all,
  hence the problem with late-model European cars
  (including the Cadillac Catera).  There are four
  different so-called stand-and-data pins in the
  standard connector, and at least four different
  types of data transmissions that could be used,
  plus enhanced version sof the standard stuff
  (other piins are available for additional
  manufacturer-specific data, such as vehicle
  diagnostic systems for a/c and ABS).